• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.1
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• pp.25-30
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• 2013

In military vehicles moving over poor roads, severe vibration of the chassis can damage internal components. Currently, many studies have focused on active and semi-active suspensions to reduce the vibration of the chassis. In this study, a vibration reduction technique is suggested by applying a unique rotating suspension structure. SH-ADD, a type of modified Skyhook, was selected as a controller for vibration reduction. A random ISO class E road was selected as the driving road. The simulation was performed using ADAMS Control and Matlab Simulink. The control result was compared with the RMS acceleration with a focus on the cumulative fatigue of the internal equipment.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.3
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• pp.214-222
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• 2012

Driver's feeling is variously affected by lots of components such as engine, frame, wheels, and seats during the operation of automobiles. The main objective of this research is to identify the correlation between subjective evaluation and vibration metrics that was set by ISO to investigate development of the car vibration quality index using multiple linear regressions(MLR). A previous research related with automotive vibration quality used the method of calculating acceleration values of the point of a seat, a seat back, foot as RMS for objective evaluation. The automotive comfort is determined by RMS values. In comparison with the previous research, this study includes not only the vibration metrics, but also subjective values by jury evaluation. By indentifying the correlation between subjective evaluation and vibration metrics, the automotive vibration quality index is developed through MLR. Based on the results of this study, the proposed the automotive vibration quality index which developed through MLR will be helpful to obtain objective and reliable automotive comfort values.

• Korean Journal of Agricultural Science
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• v.30 no.2
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• pp.184-190
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• 2003

Finite element method(FEM) was used to obtain an approximate solution, since the mathematical formulations for the problem are complex and cannot be solved analytically. In this study, the fruit as well as the aluminum support on vibrator are discretized into small elements, and the approximate functions are used to describe the displacements in each element in terms of nodal values, and because of the complexity of the problem of viscoelastic materials such as the fruit and vegetables, it was necessary to validate the modeling approach before pear simulations were performed, and the finite element modeling approach was first validated by comparing the results obtained from simulation and experiment for the pear in the frequency range 3 to 150 Hz and acceleration level of 0.25 G-rms. Based on the relatively good agreement between simulated and measured frequencies for the pear, finite element models of tomato and oriental melon were created to study the vibration characteristics of the fruit and vegetables. The resonance frequencies of the pear, tomato and oriental melon using FEM were 62.50, 39.45 and 62.73 Hz and the peak accelerations of them using FEM were 2.21, 1.38 and 1.98 G-rms.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.683-688
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• 2012

Driver's feeling is variously affected by lots of components such as engine, frame, wheels, and seats during the operation of automobiles. The main objective of this research is to identify the correlation between subjective evaluation and vibration metrics that was set by ISO to investigate development of the car vibration quality index using multiple linear regressions (MLR). A previous research related with automotive vibration quality used the method of calculating acceleration values of the point of a seat, a seat back, foot as RMS for objective evaluation. The automotive comfort is determined by RMS values. In comparison with the previous research, this study includes not only the vibration metrics, but also subjective values by jury evaluation. By indentifying the correlation between subjective evaluation and vibration metrics, the automotive vibration quality index is developed through MLR. Based on the results of this study, the proposed the automotive vibration quality index which developed through MLR will be helpful to obtain objective and reliable automotive comfort values.

• Wind and Structures
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• v.13 no.6
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• pp.499-517
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• 2010

Advances in structural materials and construction methods have resulted in flexible and light tall buildings, making an assessment of structural safety during strong wind and serviceability/habitability during comparable medium/weak wind important design criteria. So far, lots of studies on suppressing the wind-induced responses have been carried out for tall buildings with aerodynamic modification. Most of the studies on aerodynamic modification have forced on the corner modification, while the studies on taper and set-back are limited. Changes of sectional shape through taper and set-back can modify the flow pattern around the models, encouraging more 3-dimensionalities, which results in reducing the wind-induced excitations. This paper discusses the characteristics of overturning moments and wind-induced responses of the tall buildings with height variations. The reduction of mean along-wind and fluctuating across-wind overturning moments are apparent in the suburban area than in urban area. A series of the response analyses, the rms displacement responses of the tall buildings with height variations are reduced greatly, while the rms acceleration responses are not necessarily reduced, showing dependences on wind direction.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.1099-1102
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• 2017

High frequency signals are analyzed which are measured at the inlet / outlet pipeline and pump casing during cavitation tests of the fuel pump for the liquid rocket engine. RMS values of each data are shown according to the cavitation number and compared with those of the LOx pump tests and the impact of the cavitation instability is also explored. Analogies about the cavitation number are confirmed between high frequency data of both pumps. In addition, the cavitation instability is found in all the signals and has an affect on the outlet pressure pulsation of the fuel pump.

• Journal of the Korean Society of Safety
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• v.29 no.1
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• pp.15-20
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• 2014

The silicon as the hyper-elastic material was used to design the shock programmer and dynamic characteristic of the shock programmer was studied. The shock programmer was a structure part that was mounted between the impactor and the test bed. The role of the shock programmer was to generate the acceleration time history by the objective of various impact tests. The effective elastic modulus of the silicon was varied under the velocity of the impactor. The effective elastic modulus of the silicon was estimated by the comparison with results between test and simulation.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.3
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• pp.249-256
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• 2010

This paper presents performance analysis of a quarter-vehicle magneto-rheological(MR) suspension system with respect to different tire pressure. As a first step, MR damper is designed and manufactured based on the optimized damping force levels and mechanical dimensions required for a commercial mid-sized passenger vehicle. After experimentally evaluating dynamic characteristics of the manufactured MR damper, the quarter-vehicle MR suspension system consisting of sprung mass, spring, tire and the MR damper is constructed in order to investigate the ride comfort. After deriving the equations of the motion for the proposed quarter-vehicle MR suspension system, vertical tire stiffness with respect to different tire pressure is experimentally identified. The skyhook controller is then implemented for the realization of quarter-vehicle MR suspension system. Ride comfort characteristics such as vertical acceleration RMS and weighted RMS of sprung mass are evaluated under various road conditions.

• Physical Therapy Rehabilitation Science
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• v.11 no.3
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• pp.311-320
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• 2022

Objective: To investigate the reliability and validity of static balance measurements using an acceleration sensor and a gyroscope sensor in smart phone inertial sensors. Design: Equivalent control group pretest-posttest. Methods: Subjects were forty five healthy adults aged twenty to fifty-years-old who had no disease that could affect the experiment. After pre-test, all participants wore a waist band with smart phone, and conducted six static balance measurements on the force plate twice for 35 seconds each. To investigate the test-retest reliability of both smart phone inertial sensors, we compared the intra-correlation coefficient (ICC 3, 1) between primary and secondary measurements with the calculated root mean scale-total data. To determine the validity of the two sensors, it was measured simultaneously with force plate, and the comparision was done by Pearson's correlation. Results: The test-retest reliability showed excellent correlation for acceleration sensor, and it also showed excellent to good correlation for gyroscope sensor(p<0.05). The concurrent validity of smartphone inertial sensors showed a mostly poor to fair correlation for tandem-stance and one-leg-stance (p<0.05) and unacceptable correlation for the other postures (p>0.05). The gyroscope sensor showed a fair correlation for most of the RMS-Total data, and the other data also showed poor to fair correlation (p<0.05). Conclusions: The result indicates that both acceleration sensor and gyroscope sensor has good reliability, and that compared to force plate, acceleration sensor has unacceptable or poor correlation, and gyroscope sensor has mostly fair correlation.

• Korean Journal of Agricultural Science
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• v.32 no.1
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• pp.29-42
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• 2005

During a long journey of agricultural products from the production area to markets, the quality of agricultural products was always affected by some degree of vibration. The vibration input during the transportation may cause serious agricultural product injury, and this damage is particularly severe whenever the vegetable inside package is free to bounce, and is vibrated at its resonant frequency. The objectives of this study were to determine the resonant frequency of the oriental melon and to investigate the relationships between resonant frequency and physical properties of the oriental melon such as mass, volume and major and minor axes. In this study vibration testing device was constructed to determine the vibration response of the oriental melon in frequency ranges of 5 to 150 Hz. The computer program for controlling the vibration shaker and the function generator and measuring the vibration characteristics of the oriental melon was developed. The ranges of resonant frequency and peak acceleration at resonance of the oriental melon were 51 to 73 Hz and 1.24 to 1.92 G-rms, respectively. The resonant frequency and the peak acceleration decreased with the increase of the sample mass, volume, major and minor axes of the oriental melon. Multiple regression models for resonant frequency and peak acceleration of the oriental melon as a function of mass, major axis and minor axis of the sample were developed and analyzed.